1. Field of the Invention
The present invention relates to a projection display device for enlarging and projecting light modulated by a display element on a projection plane, and in particular, is preferably used for a projection display device in which an image on the display element is formed as an intermediate image between a projection lens section and a reflection mirror and this intermediate image is enlarged and projected by a reflection plane.
2. Description of the Related Art
Projection display devices (hereafter, referred to as “projectors”) for enlarging and projecting an image on a display element (liquid crystal panel, or the like) on a projection plane (screen, or the like) have been commercialized and widely used. In the projectors of this sort, it is desirable to reduce a distance between the screen and the projector body.
To attain this, an arrangement for oblique projection may be used in which a projection optical system is wide-angled, and at the same time, a direction of projection light traveling is oblique to an optical axis of the projection optical system. For example, when a wide-angle lens with a large view angle is used as the projection optical system, and a display element and a screen are shifted in opposite directions to each other with regard to the optical axis of the projection optical system, a projection distance is shortened, and at the same time, oblique projection without distortion can be. achieved. However, with the arrangement as mentioned, a wider-angle lens with a larger view angle is necessary, and therefore, increased costs due to a large-sized lens and a large-sized projector body pose a problem.
On the otherhand, for realization of the reduced projection distance, such an arrangement is also considered that a projection lens section and a mirror are used as a projection optical system, an image on a display element is formed as an intermediate image between the projection lens section and the mirror, and the intermediate image is then enlarged and projected by the mirror.
With the projectors of this sort, various states in use as shown in FIG. 18 are expected. With the latter arrangement, as shown in FIG. 19, since a light source, a projection lens section and a mirror are arranged in a same direction, although the light source directs in a horizontal direction for a ceiling mount type and a stationary type, the light source directs in a vertical direction for a desk mount type, thereby causing problems in a service life of the light source (burner).
By the way, according to the arrangement shown in FIG. 19, light modulated by a panel is shifted in a direction getting away from the screen with regard to an optical axis of the projection lens section (refraction optical system), and the mirror (reflection plane) is shifted in a direction opposite to the direction getting away from the screen. However, contrary to this arrangement, when the panel is shifted in a direction approaching to the screen with regard to the optical axis of the projection lens section (refraction optical system), and the mirror (reflection plane) is shifted in the direction opposite to the direction approaching to the screen, a wider angle of projection light can be further promoted.
However, with this arrangement, a level difference is created on a side surface of a main body cabinet due to shifting of the mirror with regard to the projection lens section. For this reason, when the side surface of the projector is placed on a plane to be placed (in the case of the stationary type shown in FIG. 18B), the projector will be oblique to a horizontal direction, thereby causing a problem that the light cannot be projected to the screen in a smooth manner.
This problem can be eliminated by giving the above-mentioned side surface a uniform plane without any level difference. However, this attempt will create a dead space in the main body cabinet, and such a problem arises that the projector body is large-sized.